riblet



H. J. RIBLET Feb. 14, 1956 DIRECTIONAL. COUPLING OF COAXIAL TRANSMISSION LINES 2 Sheets-Sheet 1 Filed Oct. 20, 1950 l-vs-roe HENRYJ. P/BLE'T AT 0 NEY Feb. 14, 1956 H. .1. RIBLET 2,735,070

DIRECTIONAL COUPLING OF COAXIAL. TRANSMISSION LINES Filed Oct. 20 1950 2 Sheets-Sheet 2 /N VENTOR HENRY J. P/BL E T BY A 1' NEY United States Patent DIRECTIONAL COUPLING OF COAXIAL TRANSMISSION LINES Henry J. Riblet, Wellesley Hills, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application October 20, 1950, Serial No. 191,268

3 Claims. (Cl. 333-) This invention relates to signal-wave translation systems, and more particularly to coaxial-line systems having directional couplers associated therewith.

It, is known that signal waves may be directionally coupled from one wave guide to another by the use of suitable slots'such that, if a signal wave is traveling in one direction in one wave guide, a portion of the signal will be transferred through the directional coupling slots into an adjacent guide and be propagated in said adjacent guide in substantially one direction only.

Wave guides have several disadvantages as directional couplers. First, the slots in the guides are frequency sensitive, and hence the degree of coupling and'the degree of directivity of the coupling varies considerably with frequency. Furthermore, wave guides exhibit the characteristic that they will not transfer waves whose wave length is larger than a certain critical dimension. In general, a wave guide will not support wave propagation therein of any frequency whose wave length is greater than twice the dimension of the widest side of the wave guide.

This invention discloses a structure whichwill carry waves of substantially all frequencies and will exhibit directive coupling characteristics which are substantially constantover a wider band of frequencies than was pre- .viously possible with waveguide structures.

Briefly, this is accomplished by the use ofycoa-xial lines as the wave-transferring structures with a:directive coupling between the coaxial lines. In one embodiment, a pair of coaxial lines has its outer walls intersecting each other at substantiallyright angles. At the point of intersection, a pair of cross slots is cut through the walls of both coaxiallines. Sinceeach of the slots couples, to a substantial degree, with energy in one of the lines only, a probe is placedadjacentthe slot inthe other line to produce coupling thereto.

.In another embodiment ofthe invention, a directive coupling is produced .by inserting a probe in the first coaxiallinc and.connectingsaidprobe-to a loop in the second. of saidcoaxial lines. Similarly, a loop inthe first coaxial line is connected to-a probe in the second coaxial line. The loops lie in planes which are substantially parallel to-the axes of; their coaxial lines. Since the loop will radiate in some degree asymmetrically; while the probe radiates symmetrically, the radiated waves will cancel out in one direction and add up in the other direction.

Other and further advantages of the invention will be apparent as the description thereof progresses, reference being had to the accompanying drawings, wherein:

Fig. 1 illustrates a transverse, cross-sectional view of a coaxial line directional coupler, taken along line 11 of Fig. 2;

Fig. 2 illustrates a transverse, cross-sectional view of the device shown in Fig. 1, taken along line 2-2 of Fig. 1;

Fig. 3 illustrates a perspective view of another embodiment of this invention illustrating a probe and loop type directional coupler for coaxial lines; and

2,735,070 Ce iatented Feb. 14, 1956 Fig. 4 illustrates a transverse, cross-sectional view .of the coupler shown in Fig. 3.

Referring now to Figs. 1 and 2, there is shown a first coaxial line 10 having an outer conductor 11 and an inner conductor 12. This line may be of any desired type, such as a gas-filled line whose central conductor is supported by insulating supports, or a line which is filled with a dielectric medium, such as polystyrene. Positioned adjacent line 10 and at substantially right angles thereto is a second coaxial line 13 having an outer conductor 14 and an inner conductor 15. A portion of the walls of the lines 10 and 13 intersects at the point where line 13 crosses line 10. Positioned in the intersecting portions of the outer conductors 14 and 11 is a pair of crossed slots 16 and 17, both of which extend through the intersecting Walls of each line. Slot 16 is parallel to the axis of line 10, and slot 17 is parallel to the axis of line 13. Positioned adjacent slot 17 and extending into line 13 is a metallic probe 18 which is connected to the outer wall 14 of line 13. Similarly, a probe 19 extends into line 1% from outer conductor 11 at a portion adjacent slot 16.

The operation of this structure as a directional coupler will now be described. Assume .a wave is being carried by line 10 in one direction, as indicated by the arrow 20. If this wave is the normal type of wave excitation, it will be known as a TM01 wave pattern. In this pattern, the electromagnetic lines of force surround the central .conductor in concentric circles, while the electrostatic lines extend from the central conductor outwardly to the outer conductor or from the outer conductor radially inward to the inner conductor. The currents flowing in the surface of the outer conductor for this type mode will then be parallel to the axis of the transmission line. Therefore, these currents will be substantially interrupted by the slot 17 which is transverse to the axis of the line It) and will be coupled through the slot into the line 13. The slot 16 which is parallel to the axis of the line 10 would normally interrupt substantially no current flow in the wall 11, and hence would normally not couple to the line 13. .However, due to the presence of probe 19, the current lines are sufficiently distorted to produce coupling into the .slot 16. Normally, the slot 17 being parallel to the line '13 would not radiate a .TM01 mode thereinto. .However, the presence of probe 18 in theline 13 .causesa suificient distortionofthe field to produce radiation into the line 13. The slot .16 being transverse tothe axis of line 13 requires noprobe to produce radiation thereinto.

Since the slot 17 is substantially parallel to the axis of the line 13, the radiated field along the slot will be substantially symmetricalfrom each side of the mid point of the slotaxially along line 13.. In other words, the radiation from slot 17 will besubstantially symmetrical about :slot .17 in adirection parallelto the .axis of line 13. However, slot 16 being transverse to the axis'of line .13 will radiate a wave which is asymmetrical in a direction parallel to the 'axisof line 13 about slot .16. In other words, theradiationin onedirection along line 13, due to slot 16, will be of opposite sign from the radiation in the other direction along line 13 from the slot 16, but will be of substantially equal magnitude. For this reason, since the radiation of both slots has substantially the same initial phase relationship, the wave intensities in 16 and 17 are substantially less than a half wave length of the frequencies used, the directive coupling action will be substantially unattected by variations in the frequency of the wave. Thus, it may be seen that a wide band directive coupling may be achieved by the use of coaxial lines.

Referring now to Figs. 3 and 4, another coupling structure for directional couplers using coaxial lines is shown. In this type of coupler, a pair of coaxial lines 21 and 22 is placed adjacent each other, line 21 having an outer conductor 23 and an inner conductor 24, and line 22 having an outer conductor 25 and an inner conductor 26. Outer conductors 23 and 25 touch along a portion of their outer surfaces.

Line 21 has therein a loop 27 comprising a wire, one end of which is fastened to outer conductor 23, and the other end of which passes through an insulating bushing 28, set in the outer conductors 23 and 25 at the portion where they touch, and extends into line 22 towards central conductor 26 to form a probe 29. Loop 27 lies in a plane which is parallel to the axis of line 21. Similarly, a loop 30 is positioned in line 22 adjacent probe 29, and in a plane parallel to the axis of line 22. Loop 30 comprises a wire, one end of which is connected to the outer conductor 25, and the other end of which extends through an insulating bushing 31 in outer conductors 25 and 23, and into line 21 to form a probe 32.

The operation of this device will now be described. A wave traveling in line 22, for example, in the direction of arrow 33, will have a portion thereof picked up by both loop 30 and probe 29. Loop 30 will feed the portion of'the wave through to probe 32 which will radiate a wave symmetrically axially along line 21 in both direc tions. The wave picked up by probe 29 will be fed to loop 27 positioned in line 21, and will be radiated thereby. However, a loop 27 will radiate the wave asymmetrically along the axis of line 21. In other words, the wave will be radiated in both directions along line 21 from loop 27 with a substantially equal intensity but of opposite phase. Therefore, the waves from probe 32 and loop 27 will substantially cancel in one direction, and add up in the other direction, thus producing a wave radiated in substantially one direction.

This completes the description of the embodiments of the invention illustrated herein. However, many modi fications thereof will be apparent to persons skilled in the art. For example, many different shapes and types of probes and loop couplings may be used to accomplish the directivity and couplings which rely on phase of the radiating elements to produce directivity. Therefore, it is desired that this invention be not limited to the particular details of the embodiments thereof which are described herein, except as defined by the appended claims.

What is claimed is:

l. A signal-translation system comprising a pair of substantially mutually perpendicular coaxial-transmission lines having an intersecting wall common to both said lines, each line extending in both directions along its axis beyond said intersecting wall, a signal-coupling system connected to said lines comprising a pair of mutually perpendicular slots in said intersecting wall of both lines, a first field distorting element for producing transverse current flow in the region of the crossed slots whereby an additional component of energy is coupled between said lines said first element being positioned in the outer conductor of one of said lines adjacent said slots and extending part way across the interior of said one line only, and a second field distorting element for producing transverse current flow in the region of the cross slots whereby an additional component of energy is coupled between said lines said second element being positioned in the outer conductor of the other of said lines adjacent said slots and extending part way across the interior of said other line only.

2. A signal-translation system comprising a pair of substantially mutually perpendicular coaxial-transmission lines having an intersecting wall common to both said lines, each line extending in both directions along its axis beyond said intersecting wall, a signal-coupling system connected to said lines comprising a pair of mutually perpendicular slots in said intersecting wall, a first probe for producing transverse current flow in the region of the crossed slots whereby an additional component of energy is coupled between said lines said first probe being positioned in the outer conductor of one of said lines adjacent said slots and extending part way across the interior of said one line only, and a second probe for producing the transverse current flow in the region of the crossed slots whereby an additional component of energy is coupled between said lines said second probe being positioned in the outer conductor of the other of said lines adjacent said slots and extending part way across the interior of said other line only.

3. A signal-translation system comprising a pair of substantially mutually perpendicular coaxial-transmission lines having an intersecting wall common to both said lines, each line extending in both directions along its axis beyond said intersecting wall, a signal-coupling system connected to said lines comprising a pair of mutually perpendicular intersecting slots in said intersecting wall, a pair of probes for producing transverse current flow in the region of the crossed slots whereby an additional component of energy is coupled between said lines, one of each of which is positioned in a right angle area exterior to said slots and formed by two adjacent edges of said slots, one of said probes extending only into the interior of one of said lines and the other of said probes extending only into the interior of the other of said lines.

References Cited in the file of this patent UNITED STATES PATENTS 2,423,390 Korman July 1, 1947 2,473,274 Bradley June 14, 1949 2,479,650 Tiley Aug. 23, 1949 2,532,317 Lundstrom Dec. 5, 1950 2,550,689 Gustafson May 1, 1951 2,562,281 Mumford July 31, 1951 2,636,082 Saad Apr. 21, 1953 2,641,648 Sensiper June 9, 1953 FOREIGN PATENTS 545,936 Great Britain June 18, 1942 625,378 Great Britain July 27, 1949 

